1. Field of the Invention
This invention relates to thermometers utilizing an expandable liquid to provide temperature reading, and in particular to means for permitting such thermometers to be subjected to elevated temperatures without destroying the accuracy thereof.
2. Description of the Prior Art
An improved thermometer construction is shown in my copending U.S. Patent application Ser. No. 121,269, filed Mar. 5, 1971, now U.S.Pat. No. 3,739,642, for an Open End Thermometer. Disclosed therein is an improved thermometer construction utilizing a capillary bore having an open end permitting the indicator liquid to be exposed to ambient pressure at all times while precluding flow of the indicator liquid outwardly therefrom, as a result of the outer end of the bore having a capillary cross section.
While the indicator liquid is prevented from flowing outwardly from the thermometer notwithstanding an inverted disposition thereof, if the thermometer is subjected to a temperature substantially above the normal reading temperature range, the indicator liquid may be expanded sufficiently to permit a portion thereof to pass outwardly through the open end of the capillary bore. This arrangement provides a substantial improvement over the conventional clinical thermometers having sealingly closed capillary bores as subjection of such closed thermometers to high temperatures provides substantial stresses therein which may result in shattering or exploding of the thermometers.
Because of this, it has been conventional in the clinical thermometer field to limit the temperatures at which the clinical thermometers are to be stored to 140.degree.F. or less. Such limitation has served two purposes --one, to prevent such shattering or exploding, and secondly, to prevent distortion of the glass which could destroy the necessary accuracy of the thermometer.